1. Field of the Invention
The invention concerns a method and an apparatus for optically monitoring of a knitted article during the manufacture thereof in a knitwear processing machine for faults, wherein an optical scanner scans the width of the knitted article perpendicularly to the direction of take-off and, on detection of a fault in the knitted article, indicates this and/or stops the knitwear processing machine.
2. Description of Related Art
Warp knitting machine monitors for warp knitting machines, particularly for elastic and outer garment double rib looms and terry towelling warp knitting machines, are known from the operating instructions for KW warp knitting machine monitors by the firm Erwin Sick GmbH Optik, Elektronik. These warp knitting machine monitors are used to monitor almost flat, plain-coloured knitted goods. These known warp knitting machine monitors comprise a guide rail which is disposed above the knitted article perpendicularly to its direction of travel. On the guide rail is a longitudinally movable carriage provided with a rod-like holder, at the free end of which is provided a reflex photocell head which is positioned close above the knitted article. Inside the carriage are provided electronic circuit components connected to the reflex photocell which consists of a light transmitter and a light detector. The carriage comprises a current collector connection to electrical conductors of the guide rail. The knitted article is gripped by so-called temples which are used to take off the fabric in the direction of take-off. A reflex photocell of this kind, guided by the guide rail, is moved perpendicularly to the direction of take-off of the knitted article In case of faults due to threads in the knitted article (finished article), the altered reflex behaviour is detected electrically and analysed accordingly Of course, the known warp knitting machine monitor has the advantage that the reflex photocell is disposed close above the finished knitted article in the region of the knitting tools. But it is a disadvantage that the reflex photocell cannot be moved as far as the edge of the finished article or beyond the edge of the article, as this warp knitting machine monitor is elaborate and unfavourable in its dimensions and its arrangement. Another disadvantage can be seen in that the current collector on the photocell carriage is sensitive to soiling and corrosion. Furthermore it is a disadvantage that the holder located between the reflex photocell and the photocell carriage is moved through the working zone of the knitter. It is also a disadvantage that the reflex photocell cannot be moved directly between the knitwear temple and the warp knitting tools, so that complete scanning of the knitted article is not guaranteed. It is also a disadvantage that a patterned or discontinuous knitted article cannot be monitored by means of the known warp knitting machine monitor.
From West German patent application No. 35 34 019 is known an optical web monitoring device which comprises a lighting arrangement which projects the pupil of the lighting system with a concave reflector strip into the viewing pupil of an objective lens of a diode line scan camera, in order thus to obtain the maximum possible luminous efficacy At the same time as monitoring the fabric, a fault finder with laser scanner is operated, the same reflector strips being used. This optical web monitoring device is of course used to check webs of material in which no mechanically rapidly moving optical components are to be used. The light radiated by light sources and reflected by the webs of material is to be detected by a photocell assembly with the minimum possible losses. The transmitting concave reflector which is used is dimensioned such that the light strip produced on the web of material in fact extends across the full width of the web of material. The light strip on the surface of the web of material is projected in greatly reduced form on the diode line which is provided inside the photographic camera. To produce sufficient light intensity for the diode line, the entrance pupil is projected into the lens.
This known optical web monitoring device, which is concerned mainly with projection matters and increasing efficiency of light intensity at the photocell assembly, indicates no possible solution for detecting knitwear faults due to threads in discontinuous or patterned knitwear as well. Also the optical web monitoring device is not suitable for this kind of fault detection as a result of its elaborate structure for on-line knitwear fault detection in the region of the knitting tools.